Abstract: An antenna includes first, second and third waveguides in direct communication with a base waveguide at first, second and third positions, respectively, the base waveguide forming a continuous loop. The second position, at which the second waveguide is in direct communication with the base waveguide, is spaced apart from the first position by about one-sixth the circumference of the loop. The third position, at which the third waveguide is in direct communication with the base waveguide, is spaced apart from the first position by about one-sixth the circumference of the loop, and is uninterruptedly spaced apart from the second position, without extending through the first position, by about two-thirds the circumference of the loop. The first, second and third waveguides comprise closed-channel waveguides, and the second and third waveguides have an open end and are configured to radiate electromagnetic waves and/or focus radiating electromagnetic waves.